Hey,
I always thought an arranger was someone who took a piece of music and wrote out the different parts for different instruments.
Example: if someone took a rock song and wanted an orchestra to play it, the arranger would sit down and listen to the original song, figure out the melodies, figure out the progression, and write out the sheet music for the violins, cellos, etc.
Producer roles are a-changin' fast! I think traditionally a producer was the person who saw a project from start to finish. He would choose the direction a track would go, hire the right people to get the job done, and decide when everything was ready to go. If needed, he would step in and play instruments to add his signature to a track during tracking or in post-production.
Nowadays I think producer means 'kid with an MPC and a crack of Cool Edit'.
And then there are programmers, engineers, editors...what are their roles?
They're just titles, in my opinion, a lot of roles cross different boundaries...
Nick